1. Field of the Invention
The present invention relates to a magnetic memory for reading and writing which utilizes a spin accumulation technique and which includes a magnetoresistive element.
2. Description of the Related Art
In the field of memories represented by dynamic random access memories (DRAMs), research and development of new-type memories are now progressing all over the world. The type of memories has to satisfy the following three conditions: high speed, high integration, and low energy consumption. One of the memories that is likely very successful is a magnetic random access memory (MRAM) that satisfies these conditions and has also nonvolatility.
The MRAM has a structure in which tunnel magnetoresistive (TMR) elements are arranged in an array. The TMR element has a basic structure in which two ferromagnetic layers sandwich an insulator used as a tunnel barrier. The TMR effect is a phenomenon in which the resistance of the TMR element changes to a great degree between a case where two ferromagnetic materials have parallel directions of their magnetizations and a case where two ferromagnetic materials have anti-parallel directions of their magnetizations. The research conducted in 1990s was concentrated on TMR elements with the insulator of aluminum oxide, but in recent years, more attention has been paid to the use of magnesium oxide for the insulator. There is a report that some of the TMR elements with the insulator of magnesium oxide have accomplished an effect of higher than 300%. For more information, see, for example, Jun Hayakawa, Shoji Ikeda, Young Min Lee, Ryutaro Sasaki, Toshiyasu Meguto, Fumihiro Matsukura, Hiromasa Takahashi and Hideo Ohno, “Current-Driven Magnetization Switching in CoFeB/MgO/CoFeB Magnetic Tunnel Junctions”, Jpn. J. Appl. Phys. 44, L1267 (2005).